The present embodiments relate to magnetic resonance imaging.
The activity leading to this application has received funding from the European Institute of Innovation and Technology (EIT) under grant agreement No EIT/EIT HEALTH/SGA2017/1. This European body receives support from the European Union's Horizon 2020 research and innovation program.
Especially in medical applications, such as stroke therapy, different types of imaging devices and methods, such as X-ray imaging, magnetic resonance (MR) imaging or angiography, may be useful. It is common practice in stroke therapy to use a conventional C- arm X-ray device to acquire several projection images during an intervention to provide a physician with images of, for example, a catheter and a vessel bifurcation. These projection images may be acquired from different angulations (e.g., from different perspectives, projection directions, or viewing angles) depending on an orientation of the vessel bifurcation. An ideal angulation may be determined by extracting the vessel tree using a preliminary 3D digital subtraction angiography (DSA). X-ray images may offer a higher spatial resolution, whereas MR images may offer a better soft tissue contrast.
MR images may be obtained via MR projection acquisition or by sampling a line or plane through the point of origin of k-space and Fourier-transforming the sampled data, which, according to the central slice theorem, results in a projection image. Also, an approach for generating virtual projection MR images with arbitrary angulations from a complete set of k-space data, which does not rely on ray tracing techniques, has been described by Sandy Napel, et al. in “Fast Fourier Projection for MR Angiography,” 1991 (https://doi.org/10.1002/mrm.1910190230).
It is, however, problematical that known methods result in MR images based on a parallel beam geometry, while the X-ray projection images are commonly based on a fan- or cone-beam geometry. This provides that X-ray images and MR images are not readily compatible with each other, at least not without further processing.